Unusual occurrence of a DAG motif in the Ipomovirus Cassava brown streak virus and implications for its vector transmission
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Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
PLoS ONE
Abstract
Cassava is the main staple food for over 800 million people globally. Its production in eastern
Africa is being constrained by two devastating Ipomoviruses that cause cassava brown
streak disease (CBSD); Cassava brown streak virus (CBSV) and Ugandan cassava brown
streak virus (UCBSV), with up to 100% yield loss for smallholder farmers in the region. To
date, vector studies have not resulted in reproducible and highly efficient transmission of
CBSV and UCBSV. Most virus transmission studies have used Bemisia tabaci (whitefly),
but a maximum of 41% U/CBSV transmission efficiency has been documented for this vector.
With the advent of next generation sequencing, researchers are generating whole
genome sequences for both CBSV and UCBSV from throughout eastern Africa. Our initial
goal for this study was to characterize U/CBSV whole genomes from CBSD symptomatic
cassava plants sampled in Kenya. We have generated 8 new whole genomes (3 CBSV and
5 UCBSV) from Kenya, and in the process of analyzing these genomes together with 26 previously
published sequences, we uncovered the aphid transmission associated DAG motif
within coat protein genes of all CBSV whole genomes at amino acid positions 52±54, but not
in UCBSV. Upon further investigation, the DAG motif was also found at the same positions
in two other Ipomoviruses: Squash vein yellowing virus (SqVYV), Coccinia mottle virus
(CocMoV). Until this study, the highly-conserved DAG motif, which is associated with aphid
transmission was only noticed once, in SqVYV but discounted as being of minimal importance.
This study represents the first comprehensive look at Ipomovirus genomes to determine
the extent of DAG motif presence and significance for vector relations. The presence
of this motif suggests that aphids could potentially be a vector of CBSV, SqVYV and Coc-
Mov. Further transmission and ipomoviral protein evolutionary studies are needed to confirm
this hypothesis.
Description
Keywords
DAG motif, Ipomovirus, Cassava brown streak virus, Vector transmission
Citation
Ateka E, Alicai T, Ndunguru J, Tairo F, Sseruwagi P, Kiarie S, et al. (2017) Unusual occurrence of a DAG motif in the Ipomovirus Cassava brown streak virus and implications for its vector transmission. PLoS ONE 12(11): e0187883. https://doi.org/10.1371/journal.pone.0187883